After nearly thirty years of management consulting, I consider myseslf to have good perception about client issues and to be an excellent decision maker. When is it OK to trust my instincts and when should I turn to others for verification?

Asking means you are aware that you might not be as good a decision maker as your experience might indicate. In fact, many of us overestimate our perceptiveness or decision making accuracy. Think you are a good decision maker? Let's see.

Answer the following ten questions with a numerical range (one low and one high number) that you are 90% confident contains the correct answer (i.e., there is at most a 1 in 10 chance your range is too small). Next Monday we'll provide the answers so you can see whether your decision making confidence is warranted.

Length of the Nile River (in miles)

Diameter of the moon (in miles)

Weight of an empty Airbus 380 (in pounds)

Year in which Wolfgang Amadeus Mozart was born

Gestation period of an Asian elephant (in days)

Air distance from Chicago to Shanghai (in miles)

Year the first spacecraft landed on the moon

Area of US national parks (in square miles)

Year in which Attila the Hun died

Average population density of the US (in people/sq mi)

Print out this tip and next to each numbered item write a lower and upper bound estimate (no Googling the answers!). Check back Monday.